It might change the balance, but pretty much nothing changes the CG in a plane. The CG location is determined by the characteristics of the wing, specifically at the center of the lifting force. If you think of your plane as a seesaw, the CG is the fulcrum. The fulcrum doesn't move, no matter how many kids you pile on one side (the kids, in your case, are carbon fiber rods). To balance the seesaw, you have to pile some more kids on the other side, or move the kids that are there closer to the end, or some combination of the two. Personally, when I pile a bunch of Carbon Fiber kids on one side of MY seesaw, I like to put a Bigger Battery kid on the other side to balance them. It's also fun to suddenly yank the Bigger Battery kid with no warning, and watch the Carbon Fiber kids slam their butts on the ground. Don't worry- it's OK. They're reinforced! R-R-R! (That's the Pirate Laugh version of LOL). By the way, if you DO want to change the CG location in a plane, you can move the wing forward or back on the fuselage. Good luck with that!